You probably know what you had for dinner last night—but if it was sushi, or just about any fish dish you didn’t catch yourself, maybe you shouldn’t be so sure. That’s the conclusion of a new study by the conservation group Oceana, which examined the issue of seafood fraud. You can read the full report here (PDF), but I’ll give you the short version: there’s a lot of it. DNA tests revealed that one-third of the 1,215 seafood samples collected nationwide were mislabeled. Your fish may not be the fish you wish.

That’s especially likely if you bought fish that’s labelled as snapper and tuna, both of which had the highest mislabeling rate: 87% and 59%, respectively. Sushi bars led the way in mislabeling fish—you’re more likely to get an honest catch at a grocery store—and southern California led the way in being wrong. Some of those mistakes are likely honest—a lot of fish, after all, look and even taste the same, and your corner sushi place isn’t likely to have a DNA sampler on hand. But there’s definitely some sleight of hand here. Fish labeled as “wild salmon”—usually sold at a premium—were more likely than not to actually be farmed salmon. And there are health concerns—tilefish, which can have a high mercury content that can be dangerous for pregnant women, was sold in New York as red snapper, which usually has lower mercury levels.

The National Fisheries Institute, a trade group, noted in a statement that the industry is fighting seafood fraud, though the group argued that new laws weren’t needed. The bigger problem is simply that the laws on the books for seafood fraud are rarely enforced by the Food and Drug Administration, which isn’t exactly short of responsibilities on the food safety front. The looming budget cuts in sequestration won’t help either. For now, caveat emptor is going to remain as big a part of sushi culture as soy sauce and wasabi.